Various types of coin-controlled latching mechanisms are used to control the doors of conventional dispensing units. The most common type of door-operated device is the newspaper vending machine. Conventionally such machines have detected correct coin denominations and numbers of coins using mechanical devices calibrated for the size of the coins and their overall weight.
A typical example of such a machine is disclosed in U.S. Pat. No. 3,253,690 to Brewton et al., incorporated herein by reference. In this device, the proper weight of coins inserted into the machine triggers a spring which releases a door latch, allowing the door to be opened and a newspaper to be retrieved by the customer.
Like all such vending devices, the mechanical elements that are used to open the door are moderately complex, and require constant maintenance due to normal wear or extraordinary abuse. Further, the relatching of the door also depends upon movement of the coins so that any hindrance of this movement could cause the door to remain unlocked even after it has been closed.
Upgraded versions of many vending machines use electronic coin detectors. These are usually used to trigger a switch activating a solenoid, which operates a latch to release the door so that the products behind the door can be accessed by the customer. Even with an electronic coin detecting device and the use of a solenoid to operate a latch releasing the door, overall conventional mechanical devices are complex and, thus are prone to failure.
Consequently, there exists a substantial need in the vending machine art for a simplified mechanical device that can be operated by either mechanical or electronic coin detection devices.